Time-varying frequency powered heat source

ABSTRACT

A semiconductor or other substrate can include one or more electrodes, located directly or indirectly on the substrate, separated from each other and coupled to the substrate. At the two or more electrodes, non-zero frequency time-varying electrical energy can be received. The time-varying electrical energy can be coupled via the two or more electrodes to trigger a displacement current to activate free carriers confined within the semiconductor substrate to generate frequency-controlled heat in the semiconductor substrate.

CLAIM OF PRIORITY

This application is a continuation of, and claims the benefit ofpriority of PCT Patent Application No. PCT/US2016/069490, to Anand Deo,which was filed Dec. 30, 2016, which claims the benefit of priority ofU.S. patent application Ser. No. 15/165,096, to Anand Deo, which wasfiled May 26, 2016, and which was entitled TIME-VARYING FREQUENCYPOWERED SEMICONDUCTOR SUBSTRATE HEAT SOURCE, the benefit of priority ofeach of which is hereby claimed, and each of which is herebyincorporated by reference herein in its entirety

TECHNICAL FIELD

This document relates generally to systems and methods for establishingor adjusting temperature of a semiconductor, thin film metal, or othersubstrate, such as can include establishing or adjusting non-randomtemperature gradients in time and space in the substrate andparticularly, but not by way of limitation, to substrate heating using atime-varying electric field frequency, such as for establishing anon-Brownian or non-random temperature gradient.

BACKGROUND

Many applications involve heating. Efficiency, precise control,convenience, size, and usability can be concerns with existingtechniques for establishing or adjusting temperature of a target objector space.

Spetz U.S. Pat. No. 7,429,719 provides a self-regulating heater using asemiconductor as a heating element that has a fast response and istemperature limited. A biasing network operates the semiconductor tocause the semiconductor to conduct more current at lower temperaturesand less current at higher temperatures. Spetz uses a field-effecttransistor (FET) as a heat source and then drains the resulting currentout the FET in a loop around the semiconductor in order to complete thecircuit for the pass-through current.

Wander U.S. Patent Publication No. 20110226759 discusses an example ofapplying microwaves to a semiconductor wafer to heat the semiconductorwafer. Wander uses a microwave cavity as the energy source, and merelyplaces the semiconductor in the cavity as a bulk target to be heated,without providing any ability to localize heat production or gradientsat one or more particular locations within the semiconductor substrate.

SUMMARY

The present inventor has recognized a need for improved techniques forestablishing or adjusting temperature of, or temperature gradient in, asemiconductor, thin-film metal, or other substrate (or, indirectly, thatof another object or space that is thermally coupled to thesemiconductor substrate). In this document, the term “substrate”includes the layer of material that is actively excited through anon-zero frequency time-varying electric field, and can include asemiconductor substrate, a thin-film or other substrate, a quartzsubstrate, a diamond substrate, or other suitable substrate material orcomposite material. In an illustrative but non-limiting example, thenon-zero frequency time-varying electric field can be capacitivelycoupled to a semiconductor substrate, but such coupling and such asubstrate are not requirements for certain aspects of the presentsubject matter.

This document describes, among other things, techniques for providingcontrolled time-varying excitation of a semiconductor material, such forproducing thermal energy in the semiconductor material. A non-zerofrequency time-varying electric field can be capacitively applied (in anillustrative, non-limiting example), such as via local electrodes, tothe semiconductor material. The frequency can be adjusted, such as to adesired degree of excitation, such as to induce majority carriers in thesemiconductor to oscillate to generate heat. Other techniques forintroducing energy into the semiconductor may be used in combinationwith such a technique. Such localized heat production in time and spacecan permit control or management of one or more temperature gradients inthe semiconductor substrate.

A non-limiting overview of certain aspects of the present subject matterfollows immediately below.

Aspect 1 can include or use subject matter (such as an apparatus, asystem, a device, a method, a means for performing acts, or a devicereadable medium including instructions that, when performed by thedevice, can cause the device to perform acts), such as can include oruse a semiconductor substrate. A temperature sensor can be located inassociation with the semiconductor substrate, such as to sense atemperature associated with the semiconductor substrate. Two or moreelectrodes can be located directly or indirectly on the semiconductorsubstrate. The electrodes can be separated from each other andcapacitively coupled to the semiconductor substrate. The electrodes canbe configured to receive a non-zero frequency time-varying electricalenergy such as can be capacitively coupled by the electrodes to thesemiconductor substrate such as to trigger a displacement current togenerate heat in the semiconductor substrate. The heat generation can becontrolled using information received from the temperature sensor tocontrol the time-varying energy received by the electrodes.

Aspect 2 can include or use, or can optionally be combined with thesubject matter of Aspect 1 to optionally include or use an electricfield signal generator circuit, which can be configured to generate thetime-varying electrical energy. The non-zero frequency can be at or canexceed an RF frequency or a microwave frequency such as for wired orwirelessly coupling to the electrodes. A control circuit can beconfigured to use temperature information from the temperature sensorsuch as to establish or adjust at least one of: (1) an amplitude of thetime-varying electrical energy generated by the electric field signalgenerator; (2) a frequency of the time-varying electrical energygenerated by the electric field generator; or (3) an output impedance ofthe electric field signal generator.

Aspect 3 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 2 tooptionally include or use the electric field signal generator circuitincluding an output impedance that is matched to an impedance betweenthe two or more electrodes at the specified non-zero frequency of thetime-varying electrical energy generated by the electric field signalgenerator circuit.

Aspect 4 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 3 tooptionally include or use an impedance matching circuit included in theelectric field generator or located between the electric field signalgenerator and at least one of the two or more electrodes to match, at aspecified frequency of the electric field signal generator, theimpedance between the two or more electrodes and the output impedance ofthe electric field signal generator.

Aspect 5 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 4 tooptionally include or use the two or more electrodes including first andsecond electric field nodes that can include, at a first location on thesemiconductor substrate, a spacing separating the first and secondelectrodes. The spacing can be specified to be less than or equal to aspacing capable of generating heat in the semiconductor substrate,without requiring net charge flow into or out of the semiconductorsubstrate via pass-through conduction current, in response to thetime-varying electrical energy received at the first and secondelectrodes.

Aspect 6 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 5 tooptionally include or use the one or more electrodes includingelectrically conductive material that can be separated from thesemiconductor substrate by a dielectric layer.

Aspect 7 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 5 tooptionally include or use the temperature of the substrate capable ofbeing adjusted by direct heating of the semiconductor substrate such asby an electric field produced by the capacitively-coupled time-varyingelectrical energy, without requiring indirect heat coupling to thesemiconductor substrate via the dielectric.

Aspect 8 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 7 tooptionally include or use an amplitude of the time-varying electricalenergy received by the electrodes being controlled using information,such as can be received from the temperature sensor, about thetemperature of the semiconductor substrate such as to establish oradjust the temperature of the semiconductor substrate.

Aspect 9 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 8 tooptionally include or use a frequency of the time-varying electricalenergy received by the electrodes being controlled using information,such as can be received from the temperature sensor, about thetemperature of the semiconductor substrate such as to establish oradjust the temperature of the semiconductor substrate.

Aspect 10 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 9 tooptionally include or use the two or more electrodes include a firstelectrode that is located directly or indirectly on a first face of thesemiconductor substrate and a second electrode that is located directlyor indirectly an opposing second face of the semiconductor substrate.

Aspect 11 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 10 tooptionally include or use the second electrode covering enough of theopposing second face of the semiconductor substrate to form a groundplane with respect to the first electrode.

Aspect 12 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 11 tooptionally include or use the two or more electrodes including a firstelectrode comprising a linear trace that can be located directly orindirectly on a first face of the semiconductor substrate and a secondelectrode comprising a linear trace that can be located directly orindirectly on the first face of the semiconductor substrate and that canbe separated from the first electrode by a specified distance.

Aspect 13 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 12 tooptionally include or use the specified distance being fixed (e.g.,parallel lines).

Aspect 14 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 13 tooptionally include or use the specified distance being variable such asto form a tapered arrangement (e.g., diverging or converging).

Aspect 15 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 14 tooptionally include or use a ground plane such as can be located on anopposing second face of the semiconductor substrate such as at aspecified distance from the first and second electrodes.

Aspect 16 can include or use subject matter (such as an apparatus, asystem, a device, a method, a means for performing acts, or a devicereadable medium including instructions that, when performed by thedevice, can cause the device to perform acts), or can optionally becombined with the subject matter of one or any combination of Aspects 1through 15 to optionally include or use or provide a semiconductorsubstrate and two or more electrodes, such as can be located directly orindirectly on the semiconductor substrate, such as can be separated fromeach other and capacitively coupled to the semiconductor substrate. Atthe two or more electrodes, non-zero frequency time-varying electricalenergy can be received. The time-varying electrical energy can becapacitively coupled, such as via the two or more electrodes, such as totrigger a displacement current to generate or trigger generation of heatin the semiconductor substrate. A temperature associated with thesemiconductor substrate can be sensed, such as using a temperaturesensor that can be located in association with the semiconductorsubstrate. Using information received from the temperature sensor, atemperature of the semiconductor substrate can be established oradjusted, such as by or including controlling the electrical energyreceived at the two or more electrodes.

Aspect 17 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 16 tooptionally include or use providing, such as to the two or moreelectrodes, time-varying electrical energy that can include a non-zerofrequency that can be at or can exceed at least one of a RF frequency ora microwave frequency.

Aspect 18 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 17 tooptionally include or use wirelessly receiving, such as at the two ormore electrodes, time-varying electrical energy that can include anon-zero frequency that can be at or can exceed at least one of a RFfrequency or a microwave frequency.

Aspect 19 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 18 tooptionally include or use tuning an output impedance of an electricalenergy signal generator, providing the time-varying electrical energy,such as to an impedance between the two or more electrodes at afrequency of the time-varying electrical energy generated by theelectrical energy signal generator.

Aspect 20 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 19 tooptionally include or use the establishing or adjusting a temperature ofthe semiconductor substrate, including direct heating of thesemiconductor substrate such as by an electric field produced by thetime-varying electrical energy, such as without requiring indirect heatcoupling to the substrate.

Aspect 21 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 20 tooptionally include or use, such as can comprise using temperatureinformation such as from the temperature sensor such as to establish oradjust an amplitude of the time-varying electrical energy such asreceived by the two or more electrodes.

Aspect 22 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 21 tooptionally include or use temperature information, such as from thetemperature sensor, such as to establish or adjust a frequency of thetime-varying electrical energy such as received by the two or moreelectrodes.

Aspect 23 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 22 tooptionally include or use temperature information such as from thetemperature sensor such as to adjust an impedance matching such asbetween an electric field signal generator circuit and an impedancebetween the two or more electrodes.

Aspect 24 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 23 tooptionally include or use temperature information such as from thetemperature sensor such as to control extracting heat such as from thesemiconductor substrate.

Aspect 25 can include or use subject matter (such as an apparatus, asystem, a device, a method, a means for performing acts, or a devicereadable medium including instructions that, when performed by thedevice, can cause the device to perform acts), or can optionally becombined with the subject matter of one or any combination of Aspects 1through 24 to optionally include or use or provide a substrate and oneor more electrodes, located directly or indirectly on the substrate. Theelectrodes can be configured to receive a non-zero frequencytime-varying electrical energy that can be coupled by the one or moreelectrodes to the substrate to trigger a current to generatefrequency-controlled heat in the substrate. The heat generation can becontrolled by adjusting the frequency of the time-varying electricalenergy.

Aspect 26 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 25 tooptionally include or use the one or more electrodes including two ormore electrodes including first and second electrodes separated fromeach other by different minimum spacing at different locations on atleast one of the first and second electrodes so that adjusting thefrequency of the time-varying electrical energy is capable of selectablyadjusting at least one corresponding frequency-dependent current pathbetween the first and second electrodes to provide thefrequency-controlled heat at at least one desired location in thesubstrate.

Aspect 27 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 26 tooptionally include or use the substrate including a semiconductorsubstrate. The two or more electrodes can be capacitively coupled to thesemiconductor substrate.

Aspect 28 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 27 tooptionally include or use a temperature sensor, which can be located inassociation with the substrate to sense a temperature associated withthe substrate. An electric field signal generator circuit can beconfigured to generate the time-varying electrical energy. A controlcircuit can be configured to use temperature information from thetemperature sensor to establish or adjust at least one of: (1) anamplitude of the time-varying electrical energy generated by theelectric field signal generator; (2) a frequency of the time-varyingelectrical energy generated by the electric field generator; or (3) alocation or distribution of a current path between the first and secondelectrodes.

Aspect 29 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 28 tooptionally include or use the two or more electrodes including first andsecond electric field nodes that can include, at a first location on thesemiconductor substrate, a spacing separating the first and secondelectrodes. The spacing can be specified to be less than or equal to aspacing capable of generating heat in the semiconductor substrate,without requiring net charge flow into or out of the semiconductorsubstrate via pass-through conduction current, in response to thetime-varying electrical energy received at the first and secondelectrodes.

Aspect 30 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 29 tooptionally include or use the one or more electrodes includingelectrically conductive material that can be separated from thesubstrate by a dielectric layer.

Aspect 31 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 30 tooptionally include or use the temperature of the substrate beingadjustable by direct heating of the substrate by an electric fieldproduced by the time-varying electrical energy, without requiringindirect heat coupling to the semiconductor substrate via thedielectric.

Aspect 32 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 31 tooptionally include or use an amplitude of the time-varying electricalenergy received by the one or more electrodes being controlled usinginformation about the temperature of the substrate to establish oradjust the temperature of the substrate.

Aspect 33 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 32 tooptionally include or use a frequency of the time-varying electricalenergy received by the electrodes is controlled using information aboutthe temperature of the substrate to establish or adjust the temperatureof the substrate.

Aspect 34 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 33 tooptionally include or use the two or more electrodes include a firstelectrode that is located directly or indirectly on a first face of thesemiconductor substrate and a second electrode that is located directlyor indirectly an opposing second face of the semiconductor substrate.

Aspect 35 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 34 tooptionally include or use the second electrode covering enough of theopposing second face of the semiconductor substrate to form a groundplane with respect to the first electrode.

Aspect 36 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 35 tooptionally include or use the two or more electrodes including a firstelectrode comprising a linear trace that can be located directly orindirectly on a first face of the semiconductor substrate and a secondelectrode comprising a linear trace that can be located directly orindirectly on the first face of the semiconductor substrate andseparated from the first electrode by a specified distance.

Aspect 37 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 36 tooptionally include or use the specified distance being fixed.

Aspect 38 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 36 tooptionally include or use the specified distance varying to form atapered or diverging or serpentine arrangement.

Aspect 39 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 38 tooptionally include or use a ground plane located on an opposing secondface of the semiconductor substrate at a specified distance from thefirst and second electrodes.

Aspect 40 can include or use subject matter (such as an apparatus, asystem, a device, a method, a means for performing acts, or a devicereadable medium including instructions that, when performed by thedevice, can cause the device to perform acts), or can optionally becombined with the subject matter of one or any combination of Aspects 1through 39 to optionally include or use or provide a method ofestablishing or adjusting a temperature of a heating element. Thesubject matter can comprise obtaining or providing a substrate and oneor more electrodes, which can be located directly or indirectly on thesubstrate. A non-zero frequency time-varying electrical energy can bereceived at the one or more electrodes. The time-varying electricalenergy can be controlled to trigger a current to generatefrequency-controlled heat in the substrate. A temperature of thesubstrate can be established or adjusted. This can include controllingthe frequency of the electrical energy received at the one or moreelectrodes.

Aspect 41 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 40 tooptionally include or use the obtaining or providing a substrate and oneor more electrodes comprising obtaining or providing two or moreelectrodes including first and second electrodes separated from eachother by different minimum spacing at different locations on at leastone of the first and second electrodes. The frequency of thetime-varying electrical energy can be adjusted for selectably adjustingat least one corresponding frequency-dependent current path between thefirst and second electrodes to provide the frequency-controlled heat atat least one desired location in the substrate.

Aspect 42 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 41 tooptionally include or use capacitively coupling the time-varyingelectrical energy from the one or more electrodes to the substrate.

Aspect 43 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 42 tocomprise wirelessly receiving, at the one or more electrodes,time-varying electrical energy that includes a non-zero frequency thatis at or exceeds at least one of a RF frequency or a microwavefrequency.

Aspect 44 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 43 tocomprise sensing a temperature associated with the substrate and, usinginformation about the sensed temperature, establishing or adjusting atleast one of (1) an amplitude of the time-varying electrical energygenerated by the electric field signal generator; (2) a frequency of thetime-varying electrical energy generated by the electric fieldgenerator; or (3) a location or distribution of a current path betweenthe first and second electrodes.

Aspect 45 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 44 suchthat the two or more electrodes include first and second electric fieldnodes that can include, at a first location on the semiconductorsubstrate, a spacing separating the first and second electrodes, whereinthe spacing can be specified to be less than or equal to a spacingcapable of generating heat in the semiconductor substrate, withoutrequiring net charge flow into or out of the semiconductor substrate viapass-through conduction current, in response to the time-varyingelectrical energy received at the first and second electrodes.

Aspect 46 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 45 toinclude or use establishing or adjusting a temperature of the substrate,including direct heating of the substrate by an electric field producedby the time-varying electrical energy, without requiring indirect heatcoupling to the substrate.

Aspect 47 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 46 toinclude or use temperature information to establish or adjust anamplitude of the time-varying electrical energy received by the two ormore electrodes.

Aspect 48 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 47 toinclude or use temperature information to establish or adjust afrequency of the time-varying electrical energy received by the two ormore electrodes.

Aspect 49 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 47 toinclude or use temperature information to establish or adjust animpedance matching between an electric field signal generator circuitand an impedance between the two or more electrodes.

Aspect 50 can include or use, or can optionally be combined with thesubject matter of one or any combination of Aspects 1 through 49 toinclude or use temperature information to control extracting heat fromthe substrate.

This summary is intended to provide an overview of subject matter of thepresent patent application. It is not intended to provide an exclusiveor exhaustive explanation of the invention. The detailed description isincluded to provide further information about the present patentapplication.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, which are not necessarily drawn to scale, like numeralsdescribe substantially similar components throughout the several views.Like numerals having different letter suffixes represent differentinstances of substantially similar components. The drawings illustrategenerally, by way of example, but not by way of limitation, variousembodiments discussed in the present document.

FIG. 1 shows an example of a heating or other temperature adjustmentsystem.

FIG. 2 shows an example of a system, similar to that shown in FIG. 1,that can optionally include a passive or active heat extractor.

FIG. 3 shows an example of a method of operating one or more of thesystems, or portions thereof, such as shown in FIGS. 1-2, and 4.

FIG. 4 shows an example, similar to FIGS. 1 and 2, including an optionalbiasing heater, such as can be used to pre-heat the substrate, such asto a desired temperature.

FIG. 5 shows an example of a method of operating one or more of thesystems, or portions thereof, such shown in FIGS. 1-2, and 4.

FIGS. 6-7 show examples of variation in electrode spacing, such as usingserpentine or divergent electrodes.

FIGS. 8A, 8B, 8C, 8D, 8E, and 8F show various arrangements of varioussubstrates, electrodes, and insulators.

FIG. 9A illustrates an example of changing a frequency of an appliedelectrical signal to obtain “step function” control of a localizedspatial temperature gradient.

FIG. 9B illustrates an example of changing a frequency of an appliedelectrical signal for altering a spatial distribution of the temperaturegradient, such as can include altering the locations of the maximum andminimum temperatures by shifting along the Y-axis.

DETAILED DESCRIPTION

This document describes examples of improved techniques for establishingor adjusting temperature of a semiconductor or other suitable substrate(or, indirectly, that of an object or space that is thermally coupled tothe substrate) such as for establishing or adjusting one or moretemperature gradients in the substrate.

In an illustrative, non-limiting example, the present techniques canturn a semiconductor substrate into a heat source, such as bycapacitively applying a radiofrequency (RF) or microwave or othertime-varying frequency source as the input energy. This can permitlocalized heat production, controllably variable heat production,multi-mode control of the localized heat production, and efficient heatgeneration. Localized heating can further enable establishing andmanaging one or more temperature gradients in the substrate, such as intime or space, or both.

The present techniques can use a semiconductor substrate, or one or moreother materials with free charge carriers that can remain confinedwithin the substrate, for producing thermal energy—which is differentfrom the waste thermal energy produced by a typical semiconductor logicor other integrated circuit chip, which requires pass-through current.

For example, unlike a digital or analog semiconductor integratedcircuit, the present localized heat generation apparatus and methodsneed not require an electrically conductive connection to power andground, although such power and ground inputs can be included for usewith other electrical circuits that can optionally be included on thesame integrated circuit as the present localized heat generationapparatus. By contrast, a typical digital or analog semiconductorintegrated circuit will require logic gate circuits and electricallyconductive power and ground connections.

In an example of using the present techniques, the RF or othertime-varying frequency energy can be transferred to the semiconductor orother substrate through capacitive contacts (in an illustrativenon-limiting example). The resulting process can be conceptualized as aninput conduction current, which leads to a displacement current in thefirst capacitive electrode contact, and conduction current in thesubstrate, a displacement current in the second capacitive electrodecontact, and finally a conduction current out of the second electrode tothe voltage source. Displacement current is only generated at thecapacitor contacts when an alternating voltage of nonzero frequency isapplied. An oscillating conduction current in the substrate is createdwhen the excitation is an alternating voltage of nonzero frequency. Whenviewed from a particle physics perspective, the charged particles in thesubstrate are confined to the body of the substrate and do notphysically leave the substrate through the capacitive contacts. Thecontinuity condition for current means that the displacement current inthe capacitor is equal to the conduction current in the substrate. Inthe present approach, when using a semiconductor substrate, heat isgenerated by inelastic collision of the majority carriers confinedwithin the semiconductor substrate with the semiconductor lattice andheat conduction is by the semiconductor lattice. In the presentapproach, when using a thin-film metal or other substrate, the heat iscarried by majority carriers moving in the thin film metal or othersubstrate.

The present techniques can allow multi-mode control of thermal energyproduction and the establishment of one or more thermal gradients atdesired locations in the substrate. Thermal energy production in thesemiconductor material can be accomplished by altering energy input ofthe time-varying electric field. In a first mode, this can be achievedby specifying or managing the spacing between electrodes, and/ormanaging the inductance between the electrodes either by tuning thespacing or through external circuits connected to the electrodes thatcan be used to capacitively apply a time-varying frequency to thesemiconductor. A second mode can control thermal energy production byestablishing or adjusting the frequency of the time-varying electricalsignal that is capacitively or otherwise applied to the semiconductor orother substrate. A third mode can control thermal energy production byadjusting the amplitude of the time-varying electrical signal that iscapacitively or otherwise applied to the semiconductor or othermaterial. Two or more of these modes can be used in combination witheach other, or with one or more other adjunct modes.

One or more thermal energy gradients can be established in thesemiconductor substrate using one or multiple techniques. For example,adjusting the frequency of the time-varying electrical signal beingcapacitively or otherwise applied to the semiconductor or othersubstrate via the electrodes can change a matching or couplingefficiency using such electrodes, which, in turn, can establish orcontrol one or more thermal gradients. The “match” between the appliedtime-varying electrical signal and the electrodes is a function of boththe frequency of the applied time-varying electrical signal and thespacing between electrodes at one or more locations on such electrodes.Variable thermal energy production with a particular pair of electrodescan be used to establish or adjust a localized thermal energy gradientin the semiconductor substrate, such as by specifying or adjusting aspacing between the electrodes (or respective nearest or other portionsthereof) being used to capacitively input the time-varying electricalsignal. Variation in spacing between locations on respective electrodescan be used to create a variable frequency match, for a particular inputfrequency, such as along the axis or length of the electrodes (see,e.g., spacing “S” and axis “Y” in FIGS. 6-7). This can provide variableenergy deposition along the axis of the electrodes and, consequentially,a temperature gradient along the axis of the electrodes.

Once the electrodes are in place, the spacing or geometry will remainconstant. Further control of the temperature gradient can be establishedby altering the frequency of the time-varying electrical signal beingapplied to the electrodes. The temperature gradient is a consequence ofa distribution of thermal energy bands, and associated underlyingcurrent bands, between the electrodes or between respective locations onthe respective electrodes.

In an example, a frequency change of the applied electrical energy cancreate a “step function” in the temperature gradient, in which theoverall spatial temperature gradient can remain the same in response tothe frequency change, but in which the temperature values of the maximumand minimum temperatures in the spatial temperature gradient change inresponse to the change in the applied frequency. The step function inthe spatial temperature gradient can match to the average or lumpedimpedance between the traces or electrodes, which can be treated as asingle lumped system. In a serpentine or variable-spacing electrodegeometry, it is possible that certain locations on the electrode get“turned off,” because no match exists at the applied frequency for suchlocations, therefore, no current or heat is generated at such locations.FIG. 9A illustrates an example of step function control.

In an example, a frequency change of the applied electrical energy canadditionally or alternatively alter the spatial temperature gradient byaltering the spatial distribution of the thermal and underlying currentbands between respective locations on the respective electrodes. In anexample, such altering the spatial distribution of the temperaturegradient can include altering the locations of the maximum and minimumtemperatures, e.g., shifting along the Y-axis. FIG. 9B illustrates anexample of such a frequency change altering a spatial distribution ofthe temperature gradient, such as can include altering the locations ofthe maximum and minimum temperatures by shifting along the Y-axis.Without being bound by theory, it is believed, based on current theoryand similar applications, that frequency control may be capable ofcontrolling the match at individual points of the electrodes along theY-axis.

The ability to establish spatial temperature gradient variations can bedesirable for certain applications. Depending on the geometry and sizeof the electrodes, it may not be always be possible to recognize theminute changes in spatial temperature gradients, making step functioncontrol preferred as a practical way to adjust or control suchtemperature gradients.

In the third technique, the frequency of the time-varying electricalinput signal can be altered, such as to enable a partial impedance matchthe between the electrodes to obtain the requisite energy input forobtaining the desired localized thermal energy output in the substrate.In sum, multi-modal control of localized and variable thermal energyproduction in the semiconductor substrate is possible.

The present approach to localized heating is believed to be moreefficient than heating a semiconductor within a microwave cavity. Incavity heating efficiency depends on the ratio of the size of the cavityand the target semiconductor. By contrast, the present approach requiresno cavity and offers a way to access the semiconductor continuously,such as for using the semiconductor as an active heat source, ratherthan just a target object to be heated.

FIG. 1 shows an example of a heating or other temperature adjustmentsystem 100. In an example, the system 100 can include a silicon,germanium, gallium arsenide or other semiconductor substrate 102 (orother non-semiconductor substrate material, as explained elsewhereherein). The semiconductor substrate 102 can include one or more of abulk semiconductor, a semiconductor wafer, a diced or other portion of asemiconductor wafer, etc.

Two or more electrodes 104A-B can be located indirectly on thesemiconductor substrate 102. The electrodes 104A-B can be located so asto be physically separated from each other. Such separation can includea region of the semiconductor substrate 102 generally located at leastpartially between the electrodes 104A-B. In an example, the electrodes104A-B can include metal or other electrically conductive signal traces.Such conductive signal traces can be indirectly located on thesemiconductor substrate 102, for example, such as separated therefrom byan intervening insulator or dielectric layer, such as silicon dioxide,silicon nitride, or the like. Such separation from the semiconductorsubstrate 102 by an intervening dielectric layer can permit, in anexample, capacitive coupling of a non-zero frequency time-varyingelectric field signal on the electrodes 104A-B to the semiconductorsubstrate 102. The electrodes 104A-B can be configured to receive thetime-varying electrical energy, such as can include an externallyregulated and applied non-zero frequency, such as for creating aresulting time-varying electric field in the semiconductor substrate102, such as for establishing or adjusting a local temperature of theportion of the semiconductor substrate 102 that is located in a vicinitybetween or near the electrodes 104A-B.

A temperature sensor 106 can be integrated into, formed upon, placednear, or otherwise located in association with the semiconductorsubstrate 102 or an object or space to be heated by the semiconductorsubstrate, such as to sense a temperature thereof. Informationrepresentative of the temperature of the semiconductor substrate 102 canbe provided by the temperature sensor 106, such as to a control circuit107. The control circuit 107 can be configured to control an electricfield signal generator 108, such as for use in closed-loop or othercontrol of the frequency, amplitude, or other operation of the electricfield signal generator 108. In an illustrative example, the temperaturesensor 106 can include a pn junction diode integrated into thesemiconductor substrate 102. This can provide a resultingtemperature-dependent reverse-bias pn junction diode current signal.This resulting signal can be signal-processed, such as by the controlcircuit 107, such as to provide a resulting temperature-dependentcontrol signal to the electric field signal generator 108, such for useto adjust an output frequency or amplitude or impedance matching of theelectric field signal generator 108, such as to establish or adjust atemperature of the semiconductor substrate 102 or a localized portionthereof.

The electric field signal generator 108 can include a signal generator(source) and can optionally include an impedance matching circuit. Theelectric field signal generator 108 can be operatively coupled to theelectrodes 104A-B, such as by using a wired or at least partly wirelessconnection 110A-B, such as to deliver a time-varying electric fieldsignal to the electrodes 104A-B. The time-varying electric field signalreceived by the electrodes 104A-B from the electric field signalgenerator 108 can be used to apply an AC electric field, e.g., atime-varying electric field having non-zero frequency, to a portion ofthe semiconductor substrate 102, such as to provide a resultingdisplacement current to the portion of the semiconductor substrate 102,such as to trigger heating or otherwise establish or adjust atemperature of the portion of the semiconductor substrate 102, andwithout requiring indirect heat coupling passing heat through thedielectric to the semiconductor substrate 102.

Heating the semiconductor substrate 102 by localizedcapacitively-coupled application of a non-zero frequency time-varyingelectric field does not require a net charge flowing into or out of thesemiconductor substrate. Without being bound by theory, it is believedthat the present approach of applying non-zero frequency time-varyingelectric field can induce particle motion such that majority carriers inthe semiconductor substrate 102 can oscillate bidirectionally (e.g.,back-and-forth) at the applied frequency with respect to the lattice ofthe semiconductor substrate. This is believed to produce phonons thatvibrate periodically in harmonic motion proportional to the oscillatingdisplacement current. By controlling the frequency of the non-zerofrequency applied time-varying electric field, the majority carrieroscillation can be controlled which, in turn, can control phonons andheat generation.

Such heating the semiconductor substrate 102 using the displacementcurrent by the present approach of applying a non-zero frequencytime-varying electric field is also different from inductive heating inthat, unlike inductive heating, no magnetic field need be applied. Nomagnetic-field induced eddy currents in the semiconductor substrate 102need be created. No loop or electromagnet is required to establish amagnetic field in the semiconductor substrate.

Information about the temperature of the semiconductor substrate 102,such as sensed by the temperature sensor 106, can be used to control atleast one of the amplitude or the frequency of the electric fieldgenerated by the electric field signal generator 108 and provided by theelectrodes 104A-B to the semiconductor substrate 102, and canadditionally or alternatively be used to turn the applied electric fieldon or off, such as at a desired duty cycle to attain or maintain atarget temperature of the semiconductor substrate 102, or a targettemperature of an object or space to be heated by the semiconductorsubstrate 102.

Adjusting the non-zero frequency of the applied time-varying electricfield can affect a coupling of the time-varying electric field to thesemiconductor substrate 102 and, therefore, can be used to control theconversion of the applied electric field into heating of thesemiconductor substrate 102. The applied frequency manifests itself asthe oscillating frequency of the particles inside the substrate. Theapplied frequency can range (e.g., depending on the application) such asall the way from a low frequency, for example, such as near-DC, a 60 Hzline frequency, up to a frequency in a radio frequency (RF) or microwaveor TeraHertz (THz) frequency range, or beyond. Additionally oralternatively, adjusting the amplitude of the applied electric field canaffect the power of the electric field to the semiconductor substrate102 and, therefore, can be used to control the conversion of the appliedelectric field into heating of the semiconductor substrate 102.Additionally or alternatively, one or more constructive or destructiveinterference or duty cycle or other technique can be used, such as tocontrol an amplitude of the applied non-zero electric field at a desiredlocation or region of the semiconductor substrate 102.

In an example, the two or more electrodes 104A-B shown in FIG. 1 caninclude parallel straight linear metal strip segments, such as can belocated on the same side of the bulk semiconductor substrate 102, butseparated therefrom by a silicon dioxide, silicon nitride,polytetrafluoroethylene, or other insulating dielectric layer. Suchstrips can be separated from each other by a spacing that is smallenough to be capable of generating heat in the semiconductor substrate102 in response to the displacement current provided by the non-zerofrequency applied electric field. The exact spacing for such heatgeneration may depend on the type of material of the semiconductorsubstrate 102, the type or amount of doping of the semiconductorsubstrate 102, the type or thickness of the insulator, the appliedamplitude and frequency of the non-zero frequency applied time-varyingelectric field.

Moreover, the two or more electrodes 104A-B need not be located on thesame side of the semiconductor substrate 102. In an example, at leastone of the two or more electrodes 104A-B can be located on an opposingside of the semiconductor substrate 102 from at least one other of thetwo or more electrodes 104A-B. For example, the two or more electrodes104A-B can be located on the same side of the semiconductor substrate,with a further electrode 104 on the opposite side of the semiconductorsubstrate 102, such as can be wider, e.g., to form a ground plane. Suchan approach can be useful, for example, in a balanced line excitationapproach, with V+ and V− applied to the two signal traces on the sameside of the semiconductor substrate 102, with respect to a ground plane,such as can be electrically connected to a ground or other referencevoltage, on an opposing side of the semiconductor substrate 102.

Additionally or alternatively, the two or more electrodes 104A-B canhave a tapered or variable spacing from each other, rather than thefixed spacing shown in the parallel example of FIG. 1. For example, theelectrodes 104A-B can include segments that are separated from eachother, but arranged with respect to each other at a 45 degree or otherangle, such as diverging to form a “V” but without touching each other.As explained herein, the frequency of the applied electrical signal canbe adjusted to shift the location of one or more current paths betweenthe electrodes, such as to a location at which the spacing between theelectrodes provides a certain match to the frequency. In a non-taperedexample (e.g., parallel electrodes with the same spacing therebetween atall locations on the electrodes), the frequency of the appliedelectrical signal can be adjusted to increase or decrease the amount ofheat generated by the resulting current flowing between the electrodes.

In various examples, the length of the conductive segments of theelectrodes 104A-B can extend completely across the semiconductorsubstrate 102, or can extend for a fraction of that distance, such asuntil all of the non-zero frequency applied electric field signal isabsorbed by the semiconductor substrate 102.

The line impedance presented the at least two electrodes 104A-B and thesemiconductor substrate 102 region therebetween (e.g., with or without aground plane on the opposing side of the semiconductor substrate 102)can be determined by calculation or measurement. An impedance matchingcircuit can be included between the electric field signal generator 108and the electrodes 104A-B, such as to increase or maximize powertransfer therebetween. The impedance matching circuit can include anarrow bandwidth or other impedance matching circuit that can beconfigured to match, e.g., at a specified frequency of the time-varyingelectric field signal generator 108, the line impedance presented by thetwo or more electrodes and the output impedance of the electric fieldsignal generator 108. Such an approach can enable creation of a desiredmatch without the need to adjust frequency. It can be especially usefulwhen a fixed frequency source is the only available source.

FIG. 2 shows an example of the system 200 that can optionally include apassive or active heat extractor 202. The heat extractor 202 can becoupled to one or more instances of the semiconductor substrate 102 (orone or more localized regions of the one or more instances of thesemiconductor substrate 102). The heat extractor 202 is one example ofhow to establish or optimize a thermal extraction energy pathway, suchas to help extract heat from the semiconductor substrate 102. Theextracted thermal energy can be transferred elsewhere, such as to atarget object or space. An example of a passive heat extractor 202 caninclude a heat sink. The heat sink can be selected to have good thermalconductivity, for example, higher thermal conductivity than that of thesemiconductor substrate 102. The heat sink can be integrated with thesemiconductor substrate, for example, by including metal or otherthermally conductive regions on or in the substrate. The heat sink canbe configured with one or more heat dispersion structures, such as oneor more of one or more cooling fins such as can permit radiation orconvection of heat such as away from the semiconductor substrate 102 ortoward a target object or space. The heat sink can be configured withone or more fluid channels, such as can allow liquid or other fluid flowor transport therein, such as in a partially or fully contained manner,such as in a fluid flow circuit. An active heat sink can include a fan,pump, or other active device, such as to encourage heat flow away fromthe semiconductor substrate 102. In an example, the heat extractor 202can be controlled by a signal provided by the control circuit 107, suchas based on information from the temperature sensor 106 about thetemperature of the semiconductor substrate 102 or about the targetobject or area or about the heat extractor 202 itself, depending on theselected one or more locations of one or more instances of thetemperature sensor 106.

FIG. 4 shows an example, similar to FIGS. 1 and 2, including an optionalbiasing heater 402, such as can be used to pre-heat the semiconductorsubstrate 102, such as to a desired temperature, such as at or justbelow what can be referred to as an atomic thermal equilibrium (ATE)temperature. Without being bound by theory, at the ATE temperature, itmay be easier for the applied non-zero electric field to excite themajority carriers in the semiconductor substrate into oscillation withthe semiconductor substrate to efficiently generate further thermalenergy. The biasing heater 402 can include an electric or gas-fueledheater, or a magnetic induction heater that can include a loop orelectromagnet to create eddy currents in the semiconductor substrate 102to pre-heat the semiconductor substrate 102 to ATE for then applying thenon-zero frequency time-varying electric field for generating furtherthermal energy in the semiconductor substrate 102.

The biasing heater 402 can be omitted, and the system 100 can becontrolled by the temperature sensor 106 and the control circuit 107 tooperate at or near such an ATE temperature. For example, the heatextractor 202 can include an active heat extractor that can becontrolled (e.g., in a closed-loop negative feedback arrangement) suchas to extract thermal energy from the semiconductor substrate 102 at arate that maintains a temperature of the semiconductor substrate 102 ornear an ATE temperature or other temperature at which further thermalenergy can be efficiently or most efficiently generated from thesemiconductor substrate 102.

FIG. 5 shows an example of a method 500 of operating one or more of thesystems, or portions thereof, such shown in FIGS. 1-4. At 502, atemperature of the semiconductor substrate 102 (or object or space to beheated by the semiconductor substrate) can be measured. At 504, themeasured temperature can be compared to a specified expected ATEtemperature of the semiconductor substrate 502. If the measuredtemperature is not at or above the expected ATE temperature, then at505, the semiconductor substrate 102 can be heated, and the temperaturecan be re-measured at 504. Otherwise, at 504, if the measuredtemperature is at or above the ATE temperature, a non-zero frequencytime-varying electric field can be applied to the semiconductorsubstrate 102, such as by the local electrodes that can be located onthe semiconductor substrate 102, such as separated therefrom by adielectric layer. A frequency or amplitude of the non-zero frequencytime-varying electric field can be controlled, such as to obtain adesired degree of majority-carrier oscillation induced harmonicvibration of the lattice of the semiconductor substrate, therebygenerating thermal energy in the semiconductor substrate. At 508,thermal energy can be actively or passively extracted from thesemiconductor substrate, such as for heating a target object or space.In an example, such thermal energy extraction at 508 can includethermoelectric cooling of the semiconductor substrate 102. At 510, atemperature of the semiconductor substrate can be measured. If themeasured temperature exceeds a target temperature, e.g., of thesemiconductor substrate 102, or of an object or space to be heated bythe semiconductor substrate 102, then at 512, the semiconductorsubstrate 102′ (or the target object or space) can be cooled, such as byan thermoelectric cooling device that can be integrated into thesemiconductor substrate 102. Otherwise, at 510, if the temperature ofthe semiconductor substrate 102 (or the target object or space) is notat the target temperature, then the non-zero frequency time-varyingelectric field application can continue at 506. When a desired amount ofheat has been extracted, or when a temperature of the target object orspace has been increased to be at or above a target temperature, thenthe method of 500 can be paused or can terminate.

FIG. 3 shows an example of a method 300 of operating of operating one ormore of the systems, or portions thereof, such shown in FIGS. 1,2 and 4.At 302, an electromagnetic signal generator 108 can output atime-varying signal of amplitude A and frequency F, which can becapacitively applied to the semiconductor substrate 102, such asexplained elsewhere in this document. At 304, a temperature T of thesubstrate 102, such as can be measured by the temperature sensor 106,can be provided to the control circuit 107, which at 304 can compare themeasured temperature T to a desired or reference temperature Treff. Ifthe measured temperature T is less than the reference temperature Treff,then process flow can proceed to 306. If the measured temperature T isgreater than the reference temperature Treff, then process flow canproceed to 308. If the measured temperature T is equal to the referencetemperature Treff, then process flow can return to 302. Hysteresis canbe used in the comparison, if desired.

At 306 (Treff>T), the frequency F can be increased by a specifiedincremental amount df. Then, at 310, the frequency F can be compared toa maximum frequency limit Fmax. At 310, if the incremented frequency Fdoes not exceed F max, then process flow can return to 302. Otherwise,if the incremented frequency F exceeds Fmax, then the frequency F can belimited at Fmax and process flow can continue to 312, and amplitude Acan be increased by an incremental amount da, before the process flowreturns to 302. A maximum permissible amplitude limit can be used,similar to the maximum frequency limit described.

In an example, the control circuit 107 (or other control device) cancontrol the temperature, such as by establishing or adjusting Treff,such as to a specified fixed or variable value such as depending on theneed for heat generation.

Although the present patent application has focused on using asemiconductor substrate, to which a time-varying electrical signal canbe capacitively applied to generate heat in the semiconductor substrate,the present subject matter is not so limited. Instead of (or in additionto) the semiconductor substrate, a thin-film metal substrate material(or any other material that can provide free charged particles) can beused, with a time-varying electrical signal capacitively coupledthereto. The capacitive contacts can isolate the substrate. Theassociated dielectric isolation between the input signal and thesubstrate can inhibit or prevent a short-circuit through the substrateor other similar effects. Such dielectric isolation can also help enableuse of the present techniques in applications such as in which a fire orother consequence of an electrical current short-circuit may be ofconcern.

One structure suitable for capacitively applying a time-varyingelectrical signal to a semiconductor or other substrate with electricalcharged particle carriers that are free to move within the substrate,can include a pair of parallel linear signal traces, each of length L ina direction y, and separated from each other by a separation distance s,and isolated from a first side of the substrate by a dielectric layer ofthickness t, with a conductive ground plane on the opposing second sideof the substrate. For such a structure, the line impedance (with orwithout the ground plane) can be determined by calculation and confirmedby measurement. An example of appropriate calculations is describedbelow.

For a substrate without a ground plane, using a conformal transformationand the Schwartz-Christofel transformation, it can be shown that thecapacitance and conductance of an infinitely thick substrate for theparallel trace structure can be given by the equations below, neglectingthe skin effect. In Equation 1, C₁=the capacitance in air per unitlength. In Equation 2, C₂=the capacitance of the electrodes due to thesubstrate, per unit length. In Equation 3, these capacitances C₁ and C₂add to give the total capacitance, per unit length. G=the conductance ofthe parallel trace structure, per unit length.

$\begin{matrix}{C_{1} = \frac{\text{∈}_{0}{K^{\prime}\left( k_{1} \right)}}{2\;{K\left( k_{1} \right)}}} & {{Eq}.\mspace{14mu} 1} \\{C_{2} = \frac{\text{∈}_{0}\text{∈}_{r}\;{K^{\prime}\left( k_{1} \right)}}{2\;{K\left( k_{1} \right)}}} & {{Eq}.\mspace{14mu} 2} \\{C_{total} = {C_{1} + C_{2}}} & {{Eq}.\mspace{14mu} 3}\end{matrix}$In Equations (1)-(3),

$\begin{matrix}{k_{1} = \frac{s}{s + {2\;\omega}}} & {{Eq}.\mspace{14mu} 4}\end{matrix}$

K(k₁) is the complete elliptic integral of the first kind, and

K′(k₁) is its complement

Note that:K′(k ₁)=K(k ₁′)  Eq. 5Wherek ₁′=√{square root over (1−k ₁ ²)}  Eq. 6The substrate permittivity is given as∈_(s)=∈₀∈_(r)  Eq. 7However, this expression may be complex due to its conductivityσS/m  Eq. 8In this case, the substrate permittivity becomes

$\begin{matrix}{\text{∈}_{s} = {\text{∈}_{0}\left( {\text{∈}_{r} - \frac{J\;\sigma}{\omega\text{∈}_{0}}} \right)}} & {{Eq}.\mspace{14mu} 9}\end{matrix}$where ω is the angular frequency 2πf and f is the frequency ofoperation. Then, the expressions for C₂ and C_(total) become complex andthe imaginary term is G, the conductance per unit length. If theoperating frequency f is zero, then the conductance G becomesG=σK′(k ₁)/2K(k ₁)  Eq. 10In Siemens per unit length. Also, note that if the substrate is absent,thenC _(total-air)=2C ₁.  Eq. 11The effective relative permittivity is the ratio of the capacitance ofthe structure with the substrate to the capacitance without thesubstrate, e.g., the capacitance in free space. The time-varyingfrequency guided by the electrodes will have a wave velocity given bythe ratio of c (the velocity of light in free space) and the square rootof the effective relative permittivity, that is:C/√{square root over ( )}∈_(reff)  Eq. 12provided that the substrate is non-magnetic, with a permeability ofμ_(o). Thus, the effective relative permittivity becomes

$\begin{matrix}{\in_{reff}{= {\frac{C_{total}}{C_{{total} - {air}}} = {\frac{C_{1} + C_{2}}{2C_{1}} = \frac{\left( {\text{∈}_{r} + 1} \right)}{2}}}}} & {{Eq}.\mspace{14mu} 13}\end{matrix}$The time-varying electromagnetic wave will propagate supported by theelectrodes and the substrate as:exp(Jωt−γy)  Eq 14in the y-direction, whereγ=Jω√{square root over ( )}μ ₀∈₀∈_(reff)  Eq. 15

If the wave propagation is lossless, when ε_(r) is real, then γ=jβ, isin radians/meter, and the electromagnetic wave propagates along theelectrodes as:

$\begin{matrix}{{J\;\beta} = \frac{J\;\omega\sqrt{\in_{reff}}}{C}} & {{Eq}.\mspace{14mu} 16} \\{where} & \; \\{C = {1/\sqrt{\mu_{0}\text{∈}_{0}}}} & {{Eq}.\mspace{14mu} 17}\end{matrix}$is the velocity of light in free space. If C₂ is complex, then ε_(reff)is complex, γ=α+jβ, and the attenuation term a is the real part inamperes/meter. It becomes possible to design the structure so that allof the time-varying electromagnetic power on the electrodes hasdissipated into the semiconductor substrate by the time that it hastraversed the electrode length L and reached the end. The line impedancebecomes:

$\begin{matrix}{Z_{0} = \frac{120\pi\;{K\left( k_{1} \right)}}{\sqrt{\in_{reff}}{K^{\prime}\left( k_{1} \right)}}} & {{Eq}.\mspace{14mu} 18}\end{matrix}$When ε_(reff) is complex, then the line impedance is also complex.Matching into the electrodes is possible with a careful design of thematching structure, such as can include using Eq. 18.

Finite Thickness Substrate

When the semiconductor substrate is of a finite thickness h, theequations can be slightly modified. The air capacitance term isidentical to that previously presented. However, the substratecapacitance C₂ is now changed to:

$\begin{matrix}{C^{S} = \frac{\text{∈}_{0}\left( {\text{∈}_{r} - 1} \right){K^{\prime}\left( k_{10} \right)}}{2\;{K\left( k_{10} \right)}}} & {{Eq}.\mspace{14mu} 19} \\{where} & \; \\{k_{10} = {{\tanh\left( \frac{\pi\; s}{4h} \right)}/{\tanh\left( \frac{\pi\left( {{2\omega} + s} \right)}{4h} \right)}}} & {{Eq}.\mspace{14mu} 20}\end{matrix}$Thus, the effective relative permittivity becomes:

$\begin{matrix}{\text{∈}_{reff} = {\frac{C^{a} + C^{S}}{2\; C^{a}} = {\frac{1}{2}\left( {1 + \frac{\left( {\text{∈}_{r} - 1} \right){K^{\prime}\left( k_{10} \right)}{K\left( k_{1} \right)}}{{K\left( k_{10} \right)}{K^{\prime}\left( k_{1} \right)}}} \right)}}} & {{Eq}.\mspace{14mu} 21}\end{matrix}$The propagation constant γ in radians/meter, of the electromagnetic wavealong the electrodes is given as:

$\begin{matrix}{\gamma = {\frac{J\;\omega\sqrt{\frac{C^{a} + C^{S}}{2C^{a}}}}{C} = \frac{J\;\omega\sqrt{\in_{reff}}}{C}}} & {{Eq}.\mspace{14mu} 22}\end{matrix}$Where c is the velocity of light in free space. If C^(s) is complex,then γ has an attenuation term, which is the imaginary part. It becomespossible to design the structure so that all the time-varyingelectromagnetic power on the electrodes has dissipated into thesubstrate at its end.The impedance of this line becomes

$\begin{matrix}{Z_{0} = {\sqrt{\;}\left( \frac{\mu_{0}\text{∈}_{0}}{2\;{C^{a}\left( {C^{a} + C^{S}} \right)}} \right)}} & {{Eq}.\mspace{14mu} 23}\end{matrix}$When ε_(reff) is complex, then the line impedance is also complex.

$\begin{matrix}{Z_{0} = {\sqrt{\;}\left( \frac{\mu_{0}\text{∈}_{0}}{2\;{C^{a}\left( {C^{a} + C^{S}} \right)}} \right)}} & {{Eq}.\mspace{14mu} 24}\end{matrix}$Matching into the electrodes is possible with a careful design of thematching structure, such as can include using Eq. 24.

Finite Thickness Substrate with Ground Plane

When a ground plane is used with the two parallel electrode structure,the two electrodes become coupled microstrip lines and the analyticexpressions can be used. The capacitance Cp between the two strips, andthe individual strip capacitances Cg to the ground plane can bedetermined. The coupled lines have even and odd modes, but in theexcitation model, one of the electrodes can be grounded, in which caseodd-even modes are not excited.

$\begin{matrix}{C_{g} = {2{\text{∈}_{0}\left\lbrack {\frac{\text{∈}_{r}{K\left( k_{1} \right)}}{K^{\prime}\left( k_{1} \right)} + \frac{K\left( k_{2} \right)}{K^{\prime}\left( k_{2} \right)}} \right\rbrack}}} & {{Eq}.\mspace{14mu} 25} \\{C_{p} = {{\text{∈}_{0}\left\lbrack {\frac{\text{∈}_{r}{K\left( k_{3} \right)}}{K^{\prime}\left( k_{3} \right)} + \frac{K\left( k_{4} \right)}{K^{\prime}\left( k_{4} \right)}} \right\rbrack} - {\text{∈}_{0}\left\lbrack {\frac{\text{∈}_{r}{K\left( k_{1} \right)}}{K^{\prime}\left( k_{1} \right)} + \frac{K\left( k_{2} \right)}{K^{\prime}\left( k_{2} \right)}} \right\rbrack}}} & {{Eq}.\mspace{14mu} 26} \\{k_{1} = {{\tanh\left( \frac{\pi\omega}{4h} \right)}{\tanh\left( \frac{\pi\left( {\omega + s} \right)}{4h} \right)}}} & {{Eq}.\mspace{14mu} 27} \\{k_{2} = {{\tanh\left( \frac{\pi\omega}{4\left( {h + {\pi\omega}} \right.} \right)}{\tanh\left( \frac{\pi\left( {\omega + s} \right)}{4\left( {h + {\pi\omega}} \right)} \right)}}} & {{Eq}.\mspace{14mu} 28} \\{k_{3} = {{\tanh\left( \frac{\pi\omega}{4h} \right)}{\coth\left( \frac{\pi\left( {\omega + s} \right)}{4h} \right)}}} & {{Eq}.\mspace{14mu} 29} \\{k_{4} = \frac{\omega}{\omega + s}} & {{Eq}.\mspace{14mu} 30}\end{matrix}$

When the substrate is air, it has a permitivitty of ε_(o), then theabove capacitance expressions become C_(ga) and C_(pa) with ε_(r)omitted in Equations 25 and 26. Then the expressions for the total airsubstratae capacitance Ca=Cga+Cpa and the total capacitance with thedielectric substrate present is Cd=Cg+Cp. Then the effective relativepermittivity becomes:

$\begin{matrix}{\text{∈}_{reff} = \frac{c^{d}}{c^{a}}} & {{Eq}.\mspace{14mu} 31}\end{matrix}$The impedance of the line becomes:

$\begin{matrix}{Z_{0} = \sqrt{\frac{\mu_{0}\text{∈}_{0}}{C^{a}C^{d}}}} & {{Eq}.\mspace{14mu} 32}\end{matrix}$When ∈_(reff) is complex, then the line impedance is also complex.Matching into the electrodes is possible with a careful design of thematching structure, such as can include using Eq. 32.

The equations explained above for the three example configurations canbe used to relate spacing, inductance, and frequency for mostconfigurations of the electrodes, such as for creating heat and,optionally, for establishing a temperature gradient. Such a temperaturegradient can be established by varying the spacing between electrodes—atpoints on respective electrodes that are closer together, the substratewill become hotter than at points on respective electrodes that arefarther apart. FIGS. 6-7 show examples of electrodes having variableelectrode spacing, s, between nearest points on the respectiveelectrodes. FIG. 6 shows an example of a serpentine electrodeconfiguration. FIG. 7 shows an example of a diverging linear electrodeconfiguration.

In general, for the configurations shown in FIGS. 6-7, the temperaturein the y direction will be a function of frequency, F, and separation,s, such as expressed in the following equation.T _(y)=

(F,s)  Eq. 33For each electrode geometry, one can calculate the maximum and minimummatch frequencies corresponding to the maximum and minimum spacing. Eachset of electrodes and substrate characteristics also has a triggeringfrequency for heat production. Frequencies below the triggeringfrequency do not produce heat, because there is insufficient energytransfer at such frequencies. An external impedance matching circuit canbe added in series between the time-varying electric field signalgenerator circuit 108 and the capacitive electrodes 104A-B on thesemiconductor substrate, such as to provide a desired impedance matchingto permit heat production in the semiconductor substrate at a desiredfrequency.

As shown in Eq. 33, temperature at any point y along the central axis isa function frequency (F) and spacing s. For any (frequency, spacing)combination, the temperature is maximum at location y where the match iscomplete or near complete. A gradient occurs on either side of y due tovarying degrees of matching. By altering frequency one can effectivelymove the point of maximum heat generation, and by implication thegradient, up and down along the y axis. The flow chart shown in FIG. 3describes an example of a process that can be used to control such adevice, such as to establish a desired temperature gradient. The case ofparallel electrodes is a special case in which spacing between theelectrodes is constant, and thus the percentage of matching is the samealong the entire electrode length, which does not permit a temperaturegradient in this fashion in the absence of losses occurring along thelength of the electrodes in the y-direction.

However, one can also create a temperature gradient by placing heatsinks or cooling cells at different locations on the substrate. Eachcooling cell can be controlled separately or independently, such as bythe control circuit 107 or by an external microprocessor based controlsystem that can manage the heat output of each cell to establish andmanage a temperature gradient.

For a heat production application with sufficient space and sufficientlycoarse control, the length of the electrode can be adjusted such thatall of the energy from the time-varying signal provided by the electricfield signal generator 108 can be dissipated along the length of theelectrode. A temperature gradient can be formed because the amount ofenergy transferred or left in the signal decreases as the signaltraverses the length of the electrode. Further control on heatproduction can be exercised by adjusting the amplitude of the inputsignal, such as in cases in which a maximum frequency has been reached,as explained in FIG. 3.

Example of Experimental Results

Preliminary laboratory experiments were conducted to test the viabilityof the present approach to time-varying frequency-controlled heatproduction in a semiconductor substrate.

A p-type <100> silicon semiconductor wafer substrate with resistivity inthe 15-25 ohms/cm² range was used. A 1000 Angstrom layer of silicondioxide (SiO2) was grown on a top surface of the silicon wafer. Twoparallel 1.5 centimeter long strips of copper metallization were formedupon the SiO2 on the silicon wafer as electrodes. The spacing betweenelectrodes was 1.5 millimeters in this specimen.

A Signatone probe station was used. The specimen was placed on aninsulated jig on the copper base plate of the probe station, to inhibitor prevent the base plate from acting as a heat sink. A frequencygenerator with a range of up to 900 MHz was provided for connection tothe electrodes in a quiet semi-dark room with a temperature controlledenvironment that was maintained at room temperature of 26 degreesCelsius. Any focused lamps were turned off after being used forestablishing probe contacts with the specimen. For injecting thetime-varying frequency signal onto the electrodes, an RF GGB Pico probewas used (GS configuration) to inhibit RF spatter. A 1 Watt amplifierwas placed in series with the input signal probe. An RTD temperaturesensor was used for measuring the semiconductor substrate temperatureand another was left to monitor a reference room temperaturemeasurement. Table 1, below, shows the experimental results of thechange of the temperature of the semiconductor substrate (for a singlesample of the semiconductor substrate) as a function of change offrequency of the input signal. The duration between changes in inputfrequency was set to 5 minutes to help provide steady-state data foreach frequency.

TABLE 1 Substrate Temperature vs. Frequency Frequency (MHz) Temp (C.)reading cycle 1 Temp (C.) reading cycle 2 80 No change No change 180 Nochange No change 300 No change (some change No change was seen butunable to stabilize thus was deemed inconclusive) 500 32.8 32.8 700 3433.6 900 36.8 37.4As a further verification that frequency was the only change to theoverall all experimental setup affecting the temperature changes werandomly changed frequency up and down to the values shown in the table.Each time the temperature stabilized at the same value for theparticular frequency.

In this document, the term “substrate” includes the active materiallayer that actively produces heat by the capacitively coupled non-zerofrequency time-varying electric field applied thereto. Other types ofmaterial layers may be attached to the active layer or layers, such asfor heat extraction or for one or more other application specific needs.The substrate can include a single type of semiconductor material or acomposite material, which can include multiple types of semiconductormaterials, one or more Peltier materials, or one or more otherapplication-specific materials. A composite can be created, for example,by bonding one or more types of materials though one or more bondingprocesses such as, e.g., direct bonding, glue or adhesive, etc. In anexample, a thin film metal material and a semiconductor material can bebonded together, and either or both can function as the active heatsource, such as concurrently.

Ohmic contacts can be used to operate under similar principles asdescribed herein for capacitive coupling, except without capacitivecoupling the displacement current does not occur. Still, localizedcontrol of heat generation, such as by controlling the frequency of theapplied electrical signal, is believed to be possible using ohmiccontacts as well as using capacitive contacts. FIGS. 8A-8 shows severalsubstrate examples. In FIG. 8A, capacitive electrodes 804A-B can belocated upon a semiconductor, thin-film metal, or other substrate 802,e.g., separated therefrom by an electrical insulator or dielectric layer803A-B.

In FIG. 8B, the electrical insulator 803A-B can be omitted and theelectrodes 804A-B can be located on the substrate 802, such as Schottkydiode contacts, which can include a semiconductor or thin-film metalsubstrate forming a Schottky diode connection with the electrodes804A-B.

In FIG. 8C, the substrate can include a composite substrate 802, such ascan include multiple substrates 802A-B that can be bonded together toprovide a combination of one or more substrate characteristics (e.g.,lattice alignment, doping type or concentration or both, etc.) that aresuitable for a particular application. For example, a semiconductor orthin-film metal substrate 802A, which can be bonded to a Peltiermaterial substrate 802B, such as by an electrical insulator 803A-B. Theelectrical insulator 803A-B can be thermally conductive, e.g., using abonding material having a specified thermal conductivity, which can bespecified to be higher than the thermal conductivity of one or both ofthe substrates 802A-B. In an example, the Peltier material can includebismuth telluride.

In an example, one or both of the substrates 802A-B can be activelyexcited through a capacitively coupled non-zero frequency time-varyingelectric field, such as by a set of capacitive electrodes that can beshared between the substrates 802A-B (e.g., sandwiched between thesubstrates 802A-B) or separately dedicated to a respective individualsubstrate 802A (e.g., located upon faces of the substrates 802A-B thatare opposite from an adjacent face between the substrates 802A-B).

FIG. 8D shows an example in which multiple electrodes 804A-B can besandwiched between the substrates 802A-B without an electrical insulatorintervening between the electrodes 804A-B and the respective substrates802A-B, such as in an arrangement in which Schottky capacitive contactsare desired.

FIG. 8E shows an example in which multiple electrodes 804A-B can besandwiched between the substrates 802A-B with a respective electricalinsulator 803A-D intervening between the electrodes 804A-B and therespective substrates 802A-B, such as in an arrangement in whichnon-Schottky capacitive contacts are desired.

FIG. 8F shows an example in which electrodes 804A-B are separated from athin-film metal substrate 802A by an insulator 803A-B, such as with thethin-film metal substrate 802A being deposited or otherwise formed uponan underlying supporting substrate 802B, which, in an example, caninclude a heat sink material having greater thermal conductivity thanthe thin-film metal substrate 802A and lower electrical conductivitythan the thin-film metal substrate 802A. In an example, the heat sinkmaterial of the supporting substrate 802A can include diamond or anintrinsic or lightly-doped semiconductor material.

Various Notes

The above description includes references to the accompanying drawings,which form a part of the detailed description. The drawings show, by wayof illustration, specific embodiments in which the invention can bepracticed. These embodiments are also referred to herein as “aspects” or“examples.” Such examples can include elements in addition to thoseshown or described. However, the present inventors also contemplateexamples in which only those elements shown or described are provided.Moreover, the present inventors also contemplate examples using anycombination or permutation of those elements shown or described (or oneor more aspects thereof), either with respect to a particular example(or one or more aspects thereof), or with respect to other examples (orone or more aspects thereof) shown or described herein.

In the event of inconsistent usages between this document and anydocuments so incorporated by reference, the usage in this documentcontrols.

In this document, the terms “a” or “an” are used, as is common in patentdocuments, to include one or more than one, independent of any otherinstances or usages of “at least one” or “one or more.” In thisdocument, the term “or” is used to refer to a nonexclusive or, such that“A or B” includes “A but not B,” “B but not A,” and “A and B,” unlessotherwise indicated. In this document, the terms “including” and “inwhich” are used as the plain-English equivalents of the respective terms“comprising” and “wherein.” Also, in the following claims, the terms“including” and “comprising” are open-ended, that is, a system, device,article, composition, formulation, or process that includes elements inaddition to those listed after such a term in a claim are still deemedto fall within the scope of that claim. Moreover, in the followingclaims, the terms “first,” “second,” and “third,” etc. are used merelyas labels, and are not intended to impose numerical requirements ontheir objects.

Geometric terms, such as “parallel”, “perpendicular”, “round”, or“square”, are not intended to require absolute mathematical precision,unless the context indicates otherwise. Instead, such geometric termsallow for variations due to manufacturing or equivalent functions. Forexample, if an element is described as “round” or “generally round,” acomponent that is not precisely circular (e.g., one that is slightlyoblong or is a many-sided polygon) is still encompassed by thisdescription.

Method examples described herein can be machine or computer-implementedat least in part. Some examples can include a computer-readable mediumor machine-readable medium encoded with instructions operable toconfigure an electronic device to perform methods as described in theabove examples. An implementation of such methods can include code, suchas microcode, assembly language code, a higher-level language code, orthe like. Such code can include computer readable instructions forperforming various methods. The code may form portions of computerprogram products. Further, in an example, the code can be tangiblystored on one or more volatile, non-transitory, or non-volatile tangiblecomputer-readable media, such as during execution or at other times.Examples of these tangible computer-readable media can include, but arenot limited to, hard disks, removable magnetic disks, removable opticaldisks (e.g., compact disks and digital video disks), magnetic cassettes,memory cards or sticks, random access memories (RAMs), read onlymemories (ROMs), and the like.

The above description is intended to be illustrative, and notrestrictive. For example, the above-described examples (or one or moreaspects thereof) may be used in combination with each other. Otherembodiments can be used, such as by one of ordinary skill in the artupon reviewing the above description. The Abstract is provided to complywith 37 C.F.R. § 1.72(b), to allow the reader to quickly ascertain thenature of the technical disclosure. It is submitted with theunderstanding that it will not be used to interpret or limit the scopeor meaning of the claims. Also, in the above Detailed Description,various features may be grouped together to streamline the disclosure.This should not be interpreted as intending that an unclaimed disclosedfeature is essential to any claim. Rather, inventive subject matter maylie in less than all features of a particular disclosed embodiment.Thus, the following claims are hereby incorporated into the DetailedDescription as examples or embodiments, with each claim standing on itsown as a separate embodiment, and it is contemplated that suchembodiments can be combined with each other in various combinations orpermutations. The scope of the invention should be determined withreference to the appended claims, along with the full scope ofequivalents to which such claims are entitled.

What is claimed is:
 1. An apparatus comprising: an article ofmanufacture, comprising an active heat source including: a predefinedsubstrate; and two or more electrodes, formed at manufacture to belocated directly or indirectly on the substrate, the electrodesconfigured to receive a non-zero frequency time-varying electricalenergy that is coupled by the one or more electrodes to the substrate togenerate a frequency-controlled heat source in the substrate, the heatsource location selected along a length of the two or more electrodes byadjusting the frequency of the time-varying electrical energy; andwherein the two or more electrodes include first and second electrodesseparated from each other by different minimum spacing at differentlocations on at least one of the first and second electrodes so thatadjusting the frequency of the time-varying electrical energy is capableof selectably adjusting at least one corresponding frequency-dependentcurrent path between the first and second electrodes to provide thefrequency-controlled heat at at least one desired location in thesubstrate.
 2. The apparatus of claim 1, wherein: the substrate includesa semiconductor substrate; and the two or more electrodes arecapacitively coupled to the semiconductor substrate.
 3. The apparatus ofclaim 1, comprising: a temperature sensor, located in association withthe substrate to sense a temperature associated with the substrate; anelectric field signal generator circuit, configured to generate thetime-varying electrical energy; and a control circuit, configured to usetemperature information from the temperature sensor to establish oradjust at least one of: (1) an amplitude of the time-varying electricalenergy generated by the electric field signal generator; (2) a frequencyof the time-varying electrical energy generated by the electric fieldgenerator; or (3) a location or distribution of a current path betweenthe first and second electrodes.
 4. The apparatus of claim 1, whereinthe two or more electrodes include first and second electric field nodesthat include, at a first location on the semiconductor substrate, aspacing separating the first and second electrodes, wherein the spacingis specified to be less than or equal to a spacing capable of generatingheat in the semiconductor substrate, without requiring net charge flowinto or out of the semiconductor substrate via pass-through conductioncurrent, in response to the time-varying electrical energy received atthe first and second electrodes.
 5. The apparatus of claim 1, whereinthe two or more electrodes include electrically conductive material thatis separated from the substrate by a dielectric layer.
 6. The apparatusof claim 1, wherein the temperature of the substrate is adjusted bydirect heating of the substrate by an electric field produced by thetime-varying electrical energy, without requiring indirect heat couplingto the substrate via the dielectric.
 7. The apparatus of claim 1,wherein an amplitude of the time-varying electrical energy received bythe two or more electrodes is controlled using information about thetemperature of the substrate to establish or adjust the temperature ofthe substrate.
 8. The apparatus of claim 1, wherein a frequency of thetime-varying electrical energy received by the electrodes is controlledusing information about the temperature of the substrate to establish oradjust the temperature of the substrate.
 9. The apparatus of claim 1,wherein the two or more electrodes include a first electrode that islocated directly or indirectly on a first face of the semiconductorsubstrate and a second electrode that is located directly or indirectlyan opposing second face of the semiconductor substrate.
 10. Theapparatus of claim 9, wherein the second electrode covers enough of theopposing second face of the semiconductor substrate to form a groundplane with respect to the first electrode.
 11. The apparatus of claim 1,wherein the two or more electrodes include a first electrode comprisinga linear trace that is located directly or indirectly on a first face ofthe semiconductor substrate and a second electrode comprising a lineartrace that is located directly or indirectly on the first face of thesemiconductor substrate and separated from the first electrode by aspecified distance.
 12. The apparatus of claim 11, wherein the specifieddistance is fixed.
 13. The apparatus of claim 11, wherein the specifieddistance varies to form a tapered arrangement.
 14. The apparatus ofclaim 11, comprising a ground plane located on an opposing second faceof the semiconductor substrate at a specified distance from the firstand second electrodes.
 15. The apparatus of claim 1, in which thesubstrate includes multiple layers.
 16. The apparatus of claim 1, inwhich the substrate includes multiple active layers.
 17. The apparatusof claim 1, in which the electrodes are permanently formed atmanufacture as being capacitively coupled to the active substrate,wherein the active substrate provides free charge carriers.
 18. Theapparatus of claim 1, wherein the heat source location is capable ofbeing selected by adjusting the frequency of the time-varying electricalenergy to correspond to a specified relative coplanar minimum spacing ofthe one or more electrodes along the length of the one or moreelectrodes to define the frequency-selected heat source location alongthe length of the one or more electrodes.
 19. The apparatus of claim 1,wherein the one or more electrodes include a pair of electrodes defininga variable minimum interelectrode spacing therebetween at differentlocations along a length of the one or more electrodes to allowfrequency-controlled selection of the heat source location along thelength of the one or more electrodes.
 20. A method of establishing oradjusting a temperature of a heating element, the method comprising:obtaining or providing an article of manufacture comprising an activeheat source including a predefined substrate and two or more electrodes,formed at manufacture to be located directly or indirectly on thesubstrate, wherein the two or more electrodes including first and secondelectrodes separated from each other by different minimum spacing atdifferent locations on at least one of the first and second electrodes;receiving, at the two or more electrodes, non-zero frequencytime-varying electrical energy that is coupled by the two or moreelectrodes to the substrate to generate a frequency-controlled heatsource in the substrate; tuning a frequency of the time-varyingelectrical energy to generate frequency-controlled selection of locationof heat in the substrate along a length of the two or more electrodes,the tuning including adjusting the frequency of the time-varyingelectrical energy for selectably adjusting at least one correspondingfrequency-dependent current path between the first and second electrodesto provide the frequency-controlled heat at at least one desiredlocation in the substrate; and establishing or adjusting a temperatureof the substrate, including controlling the frequency of the electricalenergy received at the two or more electrodes.
 21. The method of claim20, comprising capacitively coupling the time-varying electrical energyfrom the two or more electrodes to the substrate.
 22. The method ofclaim 20, comprising wirelessly receiving, at the two or moreelectrodes, time-varying electrical energy that includes a non-zerofrequency that is at or exceeds at least one of a RF frequency or amicrowave frequency.
 23. The method of claim 20, comprising: sensing atemperature associated with the substrate; using information about thesensed temperature, establishing or adjusting at least one of (1) anamplitude of the time-varying electrical energy generated by theelectric field signal generator; (2) a frequency of the time-varyingelectrical energy generated by the electric field generator; or (3) alocation or distribution of a current path between the first and secondelectrodes.
 24. The method of claim 20, wherein two or more electrodesinclude first and second electric field nodes that include, at a firstlocation on the substrate, a spacing separating the first and secondelectrodes, wherein the spacing is specified to be less than or equal toa spacing capable of generating heat in the substrate, without requiringnet charge flow into or out of the substrate via pass-through conductioncurrent, in response to the time-varying electrical energy received atthe first and second electrodes.
 25. The method of claim 20, wherein theestablishing or adjusting a temperature of the substrate, includesdirect heating of the substrate by an electric field produced by thetime-varying electrical energy, without requiring indirect heat couplingto the substrate.
 26. The method of claim 20, comprising usingtemperature information to establish or adjust an amplitude of thetime-varying electrical energy received by the two or more electrodes.27. The method of claim 20, comprising using temperature information toestablish or adjust a frequency of the time-varying electrical energyreceived by the two or more electrodes.
 28. The method of claim 20,comprising using temperature information to control extracting heat fromthe substrate.